Eldir
A minimal (nearly CSS-only) theme that focuses on components provided by the Hosting module and a clean administrative UI.
Seven is a backport of the default Drupal 7 administration theme (designed by Mark Boulton and Leisa Reichelt). This is simply that theme made compatible with D6 for anyone who wants to start using it now. For more information about the theme itself, visit Mark and Leisa’s Drupal 7 site at http://d7ux.org
Nerdalistic
A mix of Google and Wordpress ideas and colors in an easy to use and configure layout.
Specifically designed for making administration tasks clearer and easier to navigate, Polpo uses a fluid two column layout ideal for content editing on larger screen resolutions. This is achieved through the use of larger font sizes, clearer spacing and distinct colours to aid the usability of common tasks.
Berylizer
Berylizer is a Admin Theme for Drupal 6.x.
- xHTML, CSS2 and a little bit CSS3
- 2 column fluid layout
- Drop Down Mainmenu
Strix is a theme specifically designed for the Drupal administration pages. It is built as a sub theme of Zen,
- Clean and compact /admin overview page
- CSS based drop-down effects for the navigation menu block (see Configuration in the Readme.txt)
- Fieldsets on the node edit and node add pages are in a column to the right.
- Primitively recolorable: just change the body background color
Fruity is a clean, colorful administration theme with a small footprint
ActiveSite
Administrative-oriented theme
Bonus
The admin module provides UI improvements to the standard Drupal 6 admin interface. It implements some of the ideas being explored for usability improvements in Drupal 7.
A theme for you dead site and to use in the maintenance mode.